Picasso believed that "art is the sum of all destructions". The majority of art damage results subtly from humidity, light and pollution, but a disaster such as Hurricane Sandy results in rapid and widespread damage.

Elin Ewald, who heads O'Toole-Ewald Associates, America's top art damage appraisal company, hasn't ventured to her office on Madison Avenue for the past five days. "I haven't even stepped out of my house," she said on Wednesday morning, "but it's fair to say that this is the worst disaster affecting NYC – and its art – since 9/11. And the sheer increase in public art and art ownership in the past 10 years, which I think was largely a result of 9/11, means things may prove much worse. I especially recall dealing with the destruction by Hurricane Katrina of one whole collection of master art – these things can be truly heartbreaking."

At the American Institute for Conservation, coordinator Beth Antoine says: "We're expecting a whole lot of damage to be reported for weeks ahead." Eric Pourchot, director of institutional advancement at the American Institute for Conservation, notes, "We came about as a result of Katrina and have put much effort into educating instututions to prepare for the worst in advance of destructive weather and many collections were moved inland, indoors or upstairs. Meanwhile our Collections Emergency Response Team has had a 24-hour helpline, but I understand people have been having trouble getting through."

Outdoor art received special attention in the buildup to Sandy's arrival. The Museum of Modern Art removed statues, including Picasso's She-Goat and Katharina Fritsch's Group of Figures from the Abby Aldrich Rockerfeller Sculpture Garden and wrapped and secured others. The Public Art Fund closed and secured Tatzu Nishi's scaffolding installation around the sculpture of Columbus at Columbus Circle. The Metropolitan Museum of Art took extra precautions with its roof sculpture by Tomás Saraceno. Upstate, at the Storm King sculpture park, 15 works were removed or tethered. At the Socrates Sculpture Park in Long Island City there was until a few days ago an inflatable Buddha sculpture (Floating Echo by Chang-Jin Lee) on its lake, representing and inspiring tranquillity, but now it – and numerous other sculptures – have been removed safely.

Galleries in the Chelsea district of the city have been particularly hard hit. Magda Sawon, owner of the Postmasters gallery, tweeted: "Chelsea is flooded up to tenth avenue... Pumping the basement." With water rising, paintings not removed from walls have been badly damaged. At Zach Feuer gallery, for instance, where water reached 5ft high indoors, the exhibition Kate Levant: Closure Of the Jaw has been "destroyed". On the pavement outside Churner and Churner gallery on Tenth Avenue, soiled paintings in bubble wrap are piled up. "I've probably lost $100,000 worth of art," says owner Rachel Churner.

Gallery owners, when they are able to get to their premises, are still finding them inaccessible, with many metal doors buckled. In the Red Hook district of Brooklyn, home to many artists' studios, considerable numbers of artworks have been trashed. Sculptor and painter Z Behl lost all her work from the past two years.

The cleanup has barely begun. Conservators will repair, salvage art will be sold at knock-down prices and insurance premiums will rise. Perhaps also, Hurricane Sandy will inspire new art. Wednesday was, by coincidence, the day that artist Michel De Broin's Majestic – a sculpture made from street lamps damaged in Hurricane Katrina – was to be unveiled.